The move came under fire in the Lords from former chief inspector of prisons Lord Ramsbotham, who branded it an attempt to “suppress” the truth.

Frances Crook Chief Executive of the Howard League for Penal Reform

Lord Faulks told peers at question time: “A wide range of organisations and individuals independent of the prison service including inspectors, monitoring boards, parliamentarians and researchers are frequently given access to our prisons.

“It is right that prisons face scrutiny and are subject to public debate.

“Our priority is the welfare of prisoners, their families and those who work in prisons.

“Inaccurate and irresponsible criticisms undermine their welfare.

“Noms have the right to refuse access to those who voice such criticisms.”

Lord Ramsbotham, an independent crossbench peer, hit back, saying: “Only those who fear the truth need to try to suppress it, as the Secretary of State for Justice (Chris Grayling) is trying to do with a long-established, independent voluntary organisation whose only crimes have been to oppose him and to expose untruths.

“Can you ensure the House that this shameful instruction will be withdrawn and never again repeated in a free United Kingdom?”

Lord Faulks said that Ms Crook “disapproved of private prisons and is quoted as saying they make money out of punishing people – it is both reprehensible and immoral”.

“Just before Christmas she said on Newsnight that for a three-week period over Christmas offenders would be locked in their cells while there was as 40 per cent reduction in staff numbers,” he said.

“Both these assertions were completely wrong. She was given the opportunity to retract them, she declined to do so.

“Noms have to bear in mind the welfare of prisoners – families would be concerned at such misinformation – and the morale of prison officers.”

He said Mr Grayling had “nothing to do with the decision taken by Noms”.